I am commissioning a large delta printer I have fitted an X5 mini Everything is working except the nozzle heater. When I try to switch it on in the pronterface screen the graph indicates that it is switching on for a second of two and then back off. The heat bed works fine. I checked that the hot end thermistor was OK by removing it from the hot end and placing it on the heat bed, It tracked the heat bed thermistor perfectly. I ran the auto-tune routine and it cycled through it very quickly (the nozzle did not heat up) so how could it produce a result without an actual heat cycle? yet it produced a set of PID values.
I can see what is going on but do not know why or how to fix it.
What have I missed?

I get the feeling that something in the software is shutting it back off as soon as it is turned on. Can you give me some idea of what I could have set wrong to cause that. I downloaded a fresh copy of the bin file in case it had got messed up but no change. I assume it is a setting I have got wrong or overlooked as there are plenty of other people using it with no problems.

I built my own hot end and first put in a thermistor called a PT100 but could not find and config setup that would work for it so went back to the electronics wholesaler and go a 100K thermistor that seems to work perfectly with the default epoc settings. I can remove it from the hot end and place it on the heat bed and it will track the heat bed thermistor exactly. However I will check out the wiring in the morning as I am not prepared to knock any suggestion.
I am however still somewhat fixated on the software idea because when I turn the nozzle on, on the screen the graph showing current temp and target temp spikes up to the target for about a second and then drops back to zero

PT100 temperature sensors need a special board to work with our 3d printer controllers. E3D sells a add on board for a PT100 to make it work. Im wondering if your PID settings would maybe have something to do with the spike. It sounds like to me you have a short somewhere in the line possibly causing it to spike and maybe trigger an overheat shutoff.

If I have a short (and anything is possible as I am big on enthusiasm and not so great on electronic knowhow) how come the display shows good temperature all the time? surely there would be something showing up here too.

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